Long-term objectives include a continuation and expansion of investigations of several critical aspects of the reproductive, genetic, populational, behavioral and ecological biology and distribution of the Ixodes ticks in the I. ricinus/I. persulcatus species complex which are known to feed on humans and transmit the spirochete Borrelia burgdorferi, etiological agent of Lyme disease. These investigations will be enlarged by inclusion of reproductive and genetic investigations of I. ricinus, the major European vector, and I. persulcatus, the major Asian vector, of B. burgdorferi. Preliminary hybridization experiments among the North American I. scapularis and I. pacificus suggest a potential sterile hybrid genetic control scheme for these species, and development of this tick control method will be pursued if sterile hybrids can be produced between I. scapularis x I. ricinus and I. pacificus x I. persulcatus. Finally, tick vector-spirochete relationship studies will be expanded to include those of Russia. Specific aim (1) will expand to include hybridization attempts between 1. scapularis from the U.S. and I. ricinus from Russia and I. pacificus x I. persulcatus. Specific aim (2) will evaluate the intro- and interspecific genetic variability of each species by chromosomal analysis (including banding), isozyme and morphometric analyses and rDNA probes. Specific aim (3) will test whether sterile F1 hybrids can be produced and if so whether they can be used in a genetic tick control strategy. This will be examined via appropriate experiments. Specific aim (4) will identify and characterize local Russian habitats in which I. ricinus, I. persulcatus, and B. burgdorferi occur. Specific aim (5) will emphasize attempts to determine the natural tick vector(s) of B. burgdorferi in Russia by survey of suspect ticks and selected vertebrate hosts for presence of B. burgdorferi and vertebrate sera for presence of B. burgdorferi antibodies. Specific aim (6) will involve attempts to isolate and culture B. burgdorferi and identify tick hosts and reservoir hosts to B. burgdorferi. Techniques will involve interspecific hybridizations, chromosomal analyses, electrophoretic isozyme analyses, statistical morphometric determinations, rDNA probes, ELISA, fluorescent-antibody (FA) and indirect fluorescent antibody (IFA) techniques using monoclonal antibodies to B. burgdorferi, and spirochete culture (BSK medium).